Method of and apparatus for producing power from a heat source

ABSTRACT

A method for producing power from a heat source comprises the steps of: heating an intermediate fluid with heat from the heat source and producing a vaporized intermediate fluid in an intermediate fluid heater/vaporizer. Heat from the vaporized intermediate fluid vaporizes an organic liquid working fluid present in an organic working fluid vaporizer to form a vaporized organic working fluid and intermediate fluid condensate. The vaporized organic working fluid is expanded in an organic vapor turbine for generating power and producing expanded vaporized organic working fluid; the expanded organic vaporized working fluid being condensed to produce an organic fluid condensate with the organic fluid condensate being supplied to the organic fluid vaporizer. According to the present invention, prior to supplying the vaporized intermediate fluid to the organic fluid vaporizer the vaporized intermediate fluid is expanded in an intermediate fluid vapor turbine and power is produced.

This application is a continuation-in-part application of U.S. patentapplication Ser. Nos. 09/617,911, filed Jul. 17, 2000, and 09/702,711,filed Nov. 1, 2000, the entire contents of which are hereby incorporatedin their entirety.

TECHNICAL FIELD

This invention relates to producing power, and more particularly, to amethod of and apparatus for producing power using an intermediate fluid.

BACKGROUND OF THE INVENTION

Recently, the production of power and/or electricity and/or heat fromheat sources e.g. waste heat from gas turbines, waste heat from otherindustrial processes, combustion of certain fuels, etc. has become moreimportant. It is not always simple to produce power and/or electricityfrom such sources. In addition, high efficiency levels are not alwayseasy to attain when power is produced from these local heat sources.This is especially the case when water is not ready available or whenfreezing may occur and consequently vacuum in the power system needs tobe minimized in order to avoid air entering into the system.

It is therefore an object of the present invention to provide a new andimproved method of and apparatus for producing power wherein thedisadvantages as outlined are reduced or substantially overcome.

SUMMARY OF THE INVENTION

A method for producing power from a heat source according to the presentinvention comprises the steps of: heating an intermediate fluid withheat from said heat source and producing a vaporized intermediate fluidin an intermediate fluid heater/vaporizer. Heat from the vaporizedintermediate fluid is used to vaporize an organic liquid working fluidin an organic fluid vaporizer to form a vaporized organic working fluidand intermediate fluid condensate. According to the present inventionprior to supplying said vaporized intermediate fluid to said organicfluid vaporizer said vaporized intermediate fluid is expanded in anintermediate fluid vapor turbine and power is produced. The vaporizedorganic working fluid is expanded in an organic vapor turbine forgenerating power and producing expanded vaporized organic working fluid;the expanded organic vaporized working fluid is condensed to produce anorganic fluid condensate; and the organic fluid condensate is suppliedto the organic fluid vaporizer. The intermediate fluid condensateproduced is supplied to the intermediate fluid heater/vaporizer. Theintermediate fluid can be water or other suitable fluid(s) andpreferably, the intermediate fluid comprises an organic, alkylated heattransfer fluid. Most preferably, the intermediate fluid is a syntheticalkylated aromatic heat transfer fluid.

Furthermore, the present invention includes apparatus for producingpower from a heat source comprising: an intermediate fluidheater/vaporizer that vaporizes the intermediate fluid with heat fromsaid heat source and producing a vaporized intermediate fluid and anorganic fluid vaporizer that vaporizes an organic liquid working fluidwith heat from the vaporized intermediate fluid to form a vaporizedorganic working fluid and intermediate fluid condensate. According tothe present invention, an organic vapor turbine expands the vaporizedorganic working fluid and generates power and produces expandedvaporized organic working fluid and an organic fluid condenser condensessaid expanded organic vaporized working fluid to produce an organicfluid condensate. The organic fluid condensate is supplied to theorganic fluid vaporizer. In accordance with the present invention, anintermediate fluid vapor turbine expands said vaporized intermediatefluid prior to supplying it to said organic fluid vaporizer such thatthe intermediate fluid vapor turbine produces power. A pump supplies theintermediate fluid condensate to the intermediate fluidheater/vaporizer. The intermediate fluid can be water or other suitablefluid(s) and preferably, the intermediate fluid comprises an organic,alkylated heat transfer fluid. Most preferably, the intermediate fluidis a synthetic alkylated aromatic heat transfer fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are described by way of example,and with reference to the accompanying drawings wherein:

FIG. 1 is a schematic diagram of apparatus for producing a power inaccordance with one embodiment of the present invention;

FIG. 2 is a schematic diagram of apparatus for producing power inaccordance with another embodiment of the present invention;

FIG. 3 is a schematic diagram of apparatus for producing power inaccordance with a further embodiment of the present invention;

FIG. 4 is a schematic diagram of apparatus for producing power inaccordance with an additional embodiment of the present invention; and

FIG. 5 is a schematic diagram of apparatus for producing power inaccordance with a still further embodiment of the present invention.

FIG. 6 is a schematic diagram of apparatus for producing power inaccordance with an even further embodiment of the present invention. Allthe above-mentioned embodiments are, of course, interrelated.

Like reference numerals and designations in the various drawings referto like elements.

DETAILED DESCRIPTION

Referring now to FIG. 1, reference numeral 10 designates an embodimentof apparatus for producing power in accordance with the presentinvention. As can be seen from the drawing, the apparatus comprisesintermediate fluid heater/vaporizer 12 through which vaporizedintermediate fluid is produced using heat from heat source 13, e.g.using heat contained in hot gases, etc. The vaporized intermediate fluidis supplied to organic working fluid vaporizer 22 where it is condensedby transferring heat to organic fluid present in the vaporizer so thatvaporized organic fluid is produced. Intermediate fluid condensateproduced is returned to intermediate fluid heater/vaporizer 12 usingpump 19. The vaporized organic fluid is supplied to organic vaporturbine 24 wherein it expands and produces power. Preferably, generator26 is driven by organic vapor turbine 24 and produces electricity.Expanded vaporized organic fluid exiting organic vapor turbine 24 issupplied to organic fluid condenser 28 and organic fluid condensate isproduced. Pump 30 supplies organic fluid condensate exiting organicfluid condenser 28 to organic working fluid vaporizer 22. In accordancewith the present invention, prior to supplying vaporized intermediatefluid vaporizer 22, the vaporized intermediate fluid is supplied tointermediate fluid turbine 16 wherein the vaporized intermediate fluidexpands and produces power. Also here, preferably, intermediate fluidturbine 16 drives generator 18 that produces electricity.

In operation, intermediate fluid present in intermediate fluid vaporizer12 extracts heat from heat source 13, e.g. hot gases and intermediatefluid vapor is produced. The intermediate fluid vapor is suppliedpreferably to intermediate fluid turbine 16 and expands thereinproducing power and expanded intermediate fluid vapor exits intermediatefluid turbine 16. Since preferably, generator 18 is coupled tointermediate fluid turbine 16 electricity is produced. Expandedintermediate fluid vapor exiting intermediate fluid turbine 16 issupplied via line or conduit 20 to organic working fluid vaporizer 22.Organic working fluid present in organic working fluid vaporizer 22cools the expanded intermediate fluid vapor and intermediate fluidcondensate as well as vaporized organic working fluid is produced.Intermediate fluid condensate is supplied using pump 19 to intermediatefluid vaporizer 12. Vaporized organic working fluid is supplied toorganic working fluid turbine 24 wherein it expands and power isproduced. Expanded organic working fluid vapor exits organic workingfluid turbine 24. Preferably, organic working fluid turbine 24 iscoupled to a generator 26 and electricity is produced. The expandedorganic working fluid vapor is supplied to organic working fluidcondenser 28 that is preferably air-cooled and organic working fluidcondensate is produced. Pump 30 supplies organic working fluidcondensate to organic working fluid vaporizer 22.

The intermediate fluid can be water or other suitable fluid(s) andpreferably, the intermediate fluid comprises an organic, alkylated heattransfer fluid. Most preferably, the intermediate fluid is a syntheticalkylated aromatic heat transfer fluid. The preferred intermediate fluidis advantageous since their use avoids problems of freezing, operateswithout being at vacuum conditions and there is no need for treatment.Water usually needs treatment when used as an intermediate fluid.Preferably, the synthetic, alkylated, aromatic heat transfer fluid isuseful in a relative high temperature range: vaporizing temperaturebetween about 250° C. and about 315° C. At these temperatures, thepressure of the intermediate fluid is between about 495 kPA and 1560kPA. The relatively low pressures mentioned above make this type offluid particularly suitable for use in the present invention. Often, thecondensing temperature of the intermediate fluid on the intermediatefluid side of organic working fluid vaporizer 22 will preferably be inthe range of about 190° C. to about 140° C. but can be much lower ifneed be. Furthermore, the use of this type of intermediate fluid as aheat transfer medium for transferring heat from the heat source to theorganic working fluid and as well as producing power form theintermediate fluid increases the efficiency of the power producingsystem on a whole. Preferably, the organic working fluid comprisespentane, either n-pentane or iso-pentane.

Furthermore, if preferred organic fluid power cycle I can include apre-heater, superheater and recuperator. In addition, if preferred,generators 18 and 26 can be replaced by a single common generator drivenby turbines 16 and 24 either using dual shaft ends in the single commongenerator or through a gear drive. Most preferred, the common generatoris interposed between turbines 16 and 24.

Additionally, intermediate fluid condensate produced in organic workingfluid vaporizer 22 can be used to pre-heat the organic working fluidprior to it entering the organic working fluid vaporizer. Moreover, ifpreferred, the intermediate fluid cycle can include a recuperator. Anexample of such a cycle is shown in FIG. 2 wherein numeral 10Adesignates another embodiment of the present invention and is presentlyconsidered the best mode for carrying out the present invention. As canbe seen from the figure, numeral 21 designates an intermediate fluidrecuperator in which heat is transferred from expanded intermediatefluid vapor exiting intermediate fluid turbine 16 to intermediate fluidcondensate supplied by pump 19A from the intermediate fluid side oforganic working fluid vaporizer 22. In this embodiment, portion of theheated intermediate fluid condensate exiting intermediate fluidrecuperator 21 is supplied to organic fluid pre-heater 23 forpre-heating the organic working fluid prior to supplying it to organicworking fluid vaporizer 22. A further portion of the heated intermediatefluid condensate exiting intermediate fluid recuperator 21 is suppliedto intermediate fluid vaporizer 12. In addition, in this embodimentorganic working fluid recuperator 27 is included and is used fortransferring heat from expanded organic working fluid vapor exitingorganic working fluid turbine 24 to organic working fluid condensatesupplied by pump 30A from organic working fluid condenser 28. Heatedorganic working fluid condensate exiting organic working fluidrecuperator 27 is supplied to organic working fluid pre-heater 23. Apartfrom these items previously mentioned with reference to the presentembodiment described with relation to FIG. 2, this embodiment is similarto the embodiment described with relation to FIG. 1 and also operates ina similar manner.

Referring now to FIG. 3, numeral 10B designates a further embodiment ofthe present invention. In this embodiment, if preferred, rather thansupplying all of the intermediate fluid expanded vapor exitingintermediate fluid turbine 16 to organic working fluid vaporizer 22,only portion of the intermediate fluid expanded vapor can be supplied toorganic working fluid vaporizer 22. The other portion of theintermediate fluid expanded vapor can be supplied to suitable heat load32. Heat load 32 extracts the required heat from the other portion ofintermediate fluid expanded vapor and preferably produces intermediatefluid condensate that is returned to intermediate fluid vaporizer 12using pump 34.

Turning now to FIG. 4, numeral 10C designates an additional embodimentof the present invention. In this embodiment, if preferred, another heatload 42 can be supplied with heat from intermediate fluid condensate orportion thereof that exits organic working fluid vaporizer 22. The heatdepleted intermediate fluid condensate exiting other heat load 42 issupplied, using pump 44, to intermediate fluid heater/vaporizer 12.

In FIG. 5 numeral 10D designates a still further embodiment of thepresent invention. In this embodiment, the organic fluid power cycle iseliminated and merely intermediate power cycle 50 is used for producingpower as well as supplying heat load 52.

Referring now to FIG. 6, numeral 10E refers to a still furtherembodiment of the present invention wherein a further example of a cycleincluding a recuperator in the intermediate fluid cycle is shown. As canbe seen from the figure, numeral 21E designates an intermediate fluidrecuperator in which heat is transferred from expanded intermediatefluid vapor exiting intermediate fluid turbine 16E to intermediate fluidcondensate supplied by pump 19E from the intermediate fluid or shellside of organic working fluid vaporizer 22E. In this embodiment, portionof the intermediate fluid condensate exiting the intermediate ago fluidside of organic working fluid vaporizer 22E is supplied to organic fluidpre-heater 23E for pre-heating the organic working fluid prior tosupplying it to organic working fluid vaporizer 22E. A further portionof the intermediate fluid condensate exiting the intermediate fluid sideof organic working fluid vaporizer 22E is supplied to intermediate fluidrecuperator 21E. In the present embodiment, heat from heat source 13E isadded to the intermediate fluid condensate exiting organic pre-heater23E. Consequently, the heat transferred from the intermediate fluidcondensate to the organic working fluid in pre-heater 23E enablesfurther heat to be extracted from heat source 13E. In addition, in thisembodiment organic working fluid recuperator 27E is included and is usedfor transferring heat from expanded organic working fluid vapor exitingorganic working fluid turbine 24E to organic working fluid condensatesupplied by pump 30E from organic working fluid condenser 28E. Heatedorganic working fluid condensate exiting organic working fluidrecuperator 27E is supplied to organic working fluid pre-heater 23E.Apart from these item previously mentioned with reference to the presentembodiment described with relation to FIG. 6, this embodiment is similarto the embodiment described with relation to FIG. 1 and also operates ina similar manner.

In certain circumstances, all of the intermediate fluid exiting theintermediate fluid side of the organic working fluid vaporizer 22E canbe supplied to organic working fluid pre-heater 23E. Thereafter, thecooled intermediate fluid exiting to organic working fluid pre-heater23E can be supplied to heat source 13E, the heated intermediate fluidexiting heat source 13E being supplied to intermediate fluid recuperator21E.

Preferably, the organic working fluid for this embodiment and all otherembodiments mentioned herein comprises pentane, that is, iso-pentane andn-pentane.

In FIG. 6, generator 18E is preferably shared by the output ofintermediate turbine 16E and organic working fluid turbine 24E. This isbecause intermediate turbine 16E can operate efficiently at relativelylow rotational speeds (1500-1800 RPM), AX permitting it to be directlycoupled to generator 18E whose rotation speed is also relatively low(1500-1800 RPM). Similarly the rotational speed of organic working fluidturbine 24E can also be relatively low (1500-1800 RPM), permitting italso to be directly coupled to generator 18E. Thus generator 18E isinterposed between intermediate fluid turbine 16E and organic workingfluid turbine 24E. However, if preferred, separate generators can beprovided.

Furthermore, preferably, the embodiment described with reference to FIG.6 comprises two separate entities, heat source unit or heat recoveryvapor generator 40E and power cycle unit 50E.

Heat recovery vapor generator 40E is a once-through heater/vaporizercomprising the heater bundles and structure, exhaust gas duct-work,diverter valve and actuators, exhaust stack and by-pass stack. Thepurpose of the heat acquisition subsystem is to: a) direct andcontrol/meter the gas turbines' waste heat to the heat recovery vaporgenerator using a diverter valve; b) convert the heat contained in thecombustion gases to vapor; and c) discard the cooled combustion gases tothe atmosphere through a further exhaust stack 11E.

Heat recovery vapor generator 40E is a tube/pipe heat exchanger in whichthe intermediate fluid or thermal oil, flowing in the tubes, is heatedand vaporized by the combustion gases flowing on the shell side. Afterbeing cooled, the combustion gases are discarded to the atmospherethrough exhaust stack 11E. Heating and vaporizing occur in aonce-through heater design. This intermediate fluid or thermal oil vaporleaves the heat recovery vapor generator 40E slightly wet. The wet vaporis directed to a separator wherein its moisture is removed by a gravityseparator. Dry vapor, leaving the top of the separator, is directed tointermediate fluid or topping turbine 16E. The liquid intermediate fluidor thermal oil, leaving the bottom of the separator, is returned to theheat recovery vapor generator. The dry, separated intermediate fluid orthermal oil vapor directed to intermediate fluid turbine 16E is expandedto lower pressure. Intermediate fluid or topping turbine 16E, as well asorganic working fluid or bottoming turbine 24E are both multi-staged (2or 3 stages) axial, impulse-type turbines, preferably directly connectedto opposite ends of generator 18E, as shown. Since the intermediatefluid or thermal oil is a hydrocarbon-based fluid (like pentane), thegeometry and flow path of the intermediate fluid turbine 16E resemblesthat of organic working fluid turbine 24E.

As mentioned above, the intermediate fluid of the embodiment shown inFIG. 6 can be water or other suitable fluid(s) and preferably, theintermediate fluid comprises an organic, alkylated heat transfer fluid.Most preferably, intermediate fluid is a synthetic alkylated aromaticheat transfer fluid. While all fluids in these classes of fluids can beused as the intermediate fluid according to the present invention, themost preferred examples of the intermediate fluid at present are thethermal oils Therminol LT fluid and Dowtherm J. Therminol LT is thecommercial name for the alkyl substituted aromatic fluid of the SolutiaCompany having a center in Belgium. Dowtherm J. on the other hand is thecommercial name for a mixture of isomers of an alkylated aromatic fluidof the Dow Chemical Company being centered in the U.S.A. Fluids such asTherminol LT and Dowtherm J are stable to temperatures near 340° C. andas such are capable of better utilizing the high temperature portion ofthe gas turbine's waste heat more efficiently than pentane. Other mostpreferred examples of the intermediate fluids are isomers of diethylbenzene and mixtures of the isomers as well as butyl benzene.

It is pointed out that the intermediate fluid specified above can beused for all the embodiments mentioned herein.

Examples of heat sources from which the present invention can extractheat from are waste heat from gas turbines, waste heat from otherindustrial processes, waste heat produced in cement manufacture and inthe cement manufacturing industry, heat produced by the combustion ofbiomass fuel, etc.

Furthermore, while this specification refers to the heat transfer cycleas using an intermediate fluid, it is possible to consider, inaccordance with the present invention, the cycle using the intermediatefluid as a topping cycle with the organic working fluid cycle as abottoming cycle.

Moreover, while the embodiments of the present invention describe theuse of generators 18 or 26 or the use of a common generator forproducing electricity, in accordance with the present invention, thepower produced by turbines 16 and 24 or either of them can be used as amechanical power. Thus, for example, they can run a compressor, otherloads, etc.

While it is mentioned above that the preferred organic working fluid ispentane, that is, iso-pentane and n-pentane, other fluids such as butaneand iso-butane, hexane and iso-hexane as well as additional fluids suchas hydrocarbons, for example aliphatic parrafins in their normal andisomeric form, can be used as the working fluid for the above describedinvention and its embodiments. In addition, mixtures of the abovementioned fluids can also be used as the working fluid for the abovedescribed invention and its embodiments.

In addition, it should be noted that means mentioned in thisspecification refer to suitable means for carrying out the presentinvention.

Furthermore, it should be pointed out that the present as inventionincludes as well the method for operating the apparatus disclosed withreference to above-described figures.

It is believed that the advantages and improved results furnished by themethod and apparatus of the present invention are apparent from theforegoing description of the invention. Various changes andmodifications may be made without departing from the spirit and scope ofthe invention as described in the claims that follow.

1. A method for producing power from a heat source comprising the stepsof: a) heating a synthetic, alkylated aromatic heat transfer fluid withheat from said heat source and producing a vaporized synthetic,alkylated aromatic heat transfer fluid in an intermediate fluidheater/vaporizer; b) supplying said vaporized synthetic, alkylatedaromatic heat transfer fluid to an organic fluid vaporizer for supplyingheat to organic liquid working fluid present in said organic fluidvaporizer; c) vaporizing said organic liquid working fluid with heatfrom the vaporized synthetic, alkylated aromatic heat transfer fluid insaid organic fluid vaporizer to form a vaporized organic working fluidand a synthetic, alkylated aromatic heat transfer fluid condensate insaid organic fluid vaporizer; d) expanding said vaporized organicworking fluid in an organic vapor turbine for producing an expandedvaporized organic working fluid; e) generating power by use of anelectric generator driven by said organic vapor turbine; f) condensingsaid expanded organic vaporized working fluid to produce an organicfluid condensate; and g) supplying the organic fluid condensate to theorganic fluid vaporizer.
 2. A method according to claim 1 wherein priorto supplying said vaporized synthetic, alkylated aromatic heat transferfluid to said organic fluid vaporizer said vaporized synthetic,alkylated aromatic heat transfer fluid is expanded in an intermediatefluid vapor turbine and power is produced.
 3. A method according toclaim 1 wherein said synthetic, alkylated aromatic heat transfer fluidcondensate is supplied to said synthetic, alkylated aromatic heattransfer fluid heater/vaporizer.
 4. Apparatus for producing power from aheat source comprising: a) a synthetic, alkylated aromatic heat transferfluid heater/vaporizer that heats and vaporizes the synthetic, alkylatedaromatic heat transfer fluid with heat from said heat source andproduces a vaporized synthetic, alkylated aromatic heat transfer fluid;b) an organic fluid vaporizer that receives said vaporized synthetic,alkylated aromatic heat transfer fluid for supplying heat to an organicliquid working fluid present in said organic fluid vaporizer andvaporizes said organic liquid working fluid with heat from saidvaporized synthetic, alkylated aromatic heat transfer fluid to form avaporized organic working fluid and a synthetic, alkylated aromatic heattransfer fluid condensate in said organic fluid vaporizer; c) an organicvapor turbine that expands said vaporized organic working fluid,producing an expanded vaporized organic working fluid; d) an electricgenerator driven by said organic vapor turbine for generating power; ande) an organic fluid condenser that condenses said expanded organicvaporized working fluid to produce an organic working fluid condensateso that the organic working fluid condensate is supplied to the organicworking fluid vaporizer.
 5. Apparatus according to claim 4 including anintermediate fluid vapor turbine that expands said vaporized synthetic,alkylated aromatic heat transfer fluid prior to supplying it to saidorganic fluid vaporizer such that said intermediate fluid vapor turbineproduces power and a pump for supplying said synthetic, alkylatedaromatic heat transfer fluit condensate to said synthetic, alkylatedaromatic heat transfer fluid heater/vaporizer.
 6. Apparatus according toclaim 4 wherein said synthetic, alkylated aromatic heat transfer fluidcomprises a fluid selected from the group consisting of an alkylsubstituted aromatic fluid and a mixture of isomers of an alkylatedaromatic fluid.
 7. Apparatus according to claim 4 wherein said workingfluid comprises a working fluid selected form the group consisting ofbutane, iso-butane, n-pentane, iso-pentane, hexane, iso-hexane andmixtures thereof.